Clandestino;
From A330/A340 FCTM 8.110.4 -
In a failure situation, various combinations of ADR faults may occur, each
interpreted differently by the PRIM and FE computers:
- One ADR output is erroneous and the two remaining ADRs are correct. The PRIMs and the FEs reject the faulty ADR. On basic A333/A343 aircraft, there is no ECAM alert, however one PFD will display some incorrect parameters. On the A346 and enhanced A333 aircraft, if one ADR output is erroneous, and if this ADR is used to display the speed information on either PFD, a NAV IAS DISCREPANCY caution is triggered. In all cases, CAT3 DUAL will be displayed as an INOP SYS on the STATUS page.
- Two ADR outputs are erroneous but different and the remaining ADR is correct, or if all three ADR outputs are erroneous but different. The AP and A/THR will disconnect. If the disagreement lasts for more than 10 seconds, the PRIM triggers the NAV ADR DISAGREE ECAM caution. Flight controls revert to ALTN 2 law. The SPD LIM flag is displayed on both PFDs, however VLS and VSW are not displayed. This condition is latched until a PRIM reset is performed on ground without any hydraulic pressure. However, if the disagreement was transient, the AP and A/THR can be re-engaged when the NAV ADR DISAGREE message has disappeared.
- One ADR is correct but the other two ADRs provide the same erroneous output, or if all three ADRs provide consistent and erroneous data. The PRIMs and FEs will reject the “good” outlier ADR and will continue to operate normally using the two consistent but faulty ADRs.
The bolding is mine. The > 10 second disagreement is the trigger for ALTN 2, and it seems that the NAV ADR DISAGREE would remain for rest of the flight.
I know the quote is from A333, but I don't believe this is one of the minor differences between A332 and A333.